1. Field of the Invention
The present invention relates to an alternating current light emitting diode (i.e. AC LED) device and, more particularly, to an alternating current light emitting diode device capable of lowering total luminescent wattage to a predominant range and increasing total luminescent efficiency.
2. Description of Related Art
With reference to FIG. 1, there is shown a conventional AC LED device, which comprises a substrate 11, a plurality of LED grains 121, 122, 123, 124, and a plurality of electrical wires 131, 132, 133, 134, 135. The substrate 11 has a supporting surface 111 and two supporting elements 112 and 113 respectively locating on the two sides of the supporting surface 111; the plurality of LED grains 121, 122, 123, 124 are set on the supporting surface 111. Each of the electrical wires 132, 133, 134 provides electrical connections between the LED grains 121, 122, 123, and 124; the electrical wire 131 electrically connects the LED grain 121 with the supporting element 112, and the electrical wire 135 electrically connects the LED grain 124 with the supporting element 113. Besides, a sealed portion (not shown) may be further contained in this conventional AC LED device; the sealed portion may be set on the substrate 11 and covers the substrate 11, the LED grains 121, 122, 123, 124, and the plurality of electrical wires 131, 132, 133, 134, 135.
According to the conventional AC LED device as shown in FIG. 1, the substrate 11 is an insulated substrate, and there are four LED grains 121, 122, 123, 124 that are all AC LED grains and connected in series (tandem connection) through those electrical wires 132, 133, 134.
The said sealed portion (not shown) can function as a lens and is made of a transparent sealant; the sealed portion comprises a plurality of lenses portion (not shown) located corresponsively to the LED grains 121, 122, 123, 124; those lenses portion are set for modulating light illuminated from the LED grains 121, 122, 123, 124.
Owing to the limitation of the conventional technique for fabricating LED grains, it is impossible to precisely control the distributing positions of the illuminating wattage of each of the LED grain. As a result, precisely controlling on the total illuminating wattage of the AC LED device comprising a plurality of AC LED grains still causes considerable difficulties to those skilled in this art. Besides, in the practical situation, the real total wattage of an AC LED device is often higher than the expected one.
In order to solve this problem, a method of utilizing resistors connecting at the outer portion of the AC LED device is used to lower the total wattage of an AC LED device to a designed range. However, the excess value of the total wattage for each AC LED device is not always the same. Therefore, testing of the illumination wattage of each of the AC LED grains is needed, for selecting a resistor having proper resistance during the manufacturing process of the conventional AC LED device. As a result, the manufacturing cost is increased, and the manufacturing processe becomes more complicated.
Therefore, it is desirable to provide an improved AC LED device that has the ability for lowering the total wattage to a designed range and can increase the total illumination efficiency.